1. Field of the Invention
This invention relates to a stethoscope head for a one-way stethoscope.
2. Description of Prior Art
Although the stethoscope was introduced by T. R. H. Laennec, the founder of auscultation, almost 180 years ago, the mechanical-acoustic stethoscope still represents one of the most important and most often employed diagnostic tools in the daily practice of physicians. The diagnostic auscultation of organs, primarily the heart and the lungs, for sound phenomena provide an experienced physician with a wealth of acoustic information regarding the state of health of the patient.
The originally employed open listening tubes were replaced by the currently used stethoscopes, which has a headpiece or chest piece, with a hose system with bow-equipped ear pieces or headsets for transmitting sound to the ear. The headpieces have bell-shaped resonance bodies for receiving the body sound, which can be opened or covered by a diaphragm. Although the open resonance bodies are well suited for detecting low-frequency sound, they must be pressed tightly against the surface of a body of a patient, since the skin of the patient must close, tightly positioned with respect to the lower rim of the resonance body over its entire circumference in order to assure a satisfactory function. If the system is not closed, sound can escape to the outside, sound energy is lost and the efficiency of the stethoscope is reduced. The strong pressure of the resonance body can cause the patient pain and the skin of the patient is arched by the strong pressure and penetrates more or less deeply into the bell body. The free resonance space is reduced by this, and the resonance body must accordingly be designed relatively tall in order to prevent it from being completely filled with skin.
In connection with diaphragm-equipped resonance bodies, the sound-conducting system of the chest piece is normally closed. Therefore the headpiece does not need to be pressed on at all or only slightly during auscultation, and the rigid diaphragm rests on the skin of the patient. Since the skin and the diaphragm resting on it do not arch at all, or only slightly, the resonance body can be designed to be relatively flat. However, the rigidity of the diaphragm muffles low-frequency sounds.
To combine the advantages of both systems, two-way or even multi-way stethoscopes were developed, which have an open and a closed resonance funnel in a headpiece or even several headpieces for different frequency ranges.
Different stethoscope heads were developed for employing the advantages of diaphragm-equipped systems and for detecting low frequencies at the same time.
A two-way stethoscope head with a diaphragm which is floatingly seated is described in European Patent Reference EP-A-0 119 870. The diaphragm is loosely seated between an underside of the resonance body and the lower circumferential rim of a retaining ring fastened on the resonance body. Thus, the diaphragm can be moved up and down over a short distance, which is slightly less than its height. By varying the contact pressure, the diaphragm and the resonance body are intended to selectively form an open or a closed acoustic system and accordingly to make auscultation of low-frequency or high-frequency body sounds possible.
A stethoscope headpiece is described in U.S. Pat. No. 4,440,258, with a diaphragm that can be moved in the vertical direction between two relative positions with respect to the resonance body, wherein the acoustic rigidity of the diaphragm is changed and the stethoscope can be tuned to different frequency levels.
An adapter made of an elastomeric material for a stethoscope head is described in U.S. Pat. No. 4,995,473, which encloses the basic range of the stethoscope head. The hollow-cylindrical adapter tapers toward the side facing the patient. If the stethoscope head having the adapter is placed on the body surface of the patient, the air space between the body surface and the diaphragm is sealed in a soundproof manner against the outside without the diaphragm coming into contact with the body surface.
An ergonometric breast piece of a stethoscope is known from European Patent Reference EP-A-0 500 279. A raised centerpiece with two lateral recessed grips is placed on the resonance body to ease grasping and holding of the stethoscope head and to simultaneously make possible the operation of control elements, which are attached to the centerpiece for controlling the volume.
Great demands are made on the stethoscope and also on the examining physician in the course of detecting and evaluating the acoustic signals. To be able to make optimal use of the acoustic information and therefore to prevent wrong diagnoses, a great deal of experience on the part of the physician is required and the signal provided by the stethoscope must be of high quality, reproducible and as free as possible of external interference signals.
To facilitate and aid the diagnosis, it has been attempted for some time to acoustically amplify the noise emanating from the body using microphones and amplifiers. The use of microcomputers and custom-made diagnostic software in phonocardiography is a further step in making the interpretation of the sound phenomena easier. The increasing miniaturization of electronic and computer components provides for such systems, which are integrated into handy devices, in the ideal case in a slightly enlarged stethoscope head.
Whether the direct sound is evaluated in the customary manner, or a signal transformed with computer assistance into electrical voltage changes, the quality of the received information is decisively dependent on the acoustic signal primarily received on the surface of the body. This primary signal is negatively affected by various factors. Noise from the surroundings is received and passed on by the resonance body. Noises, which are generated on a body surface of a patient in the form of substrate noises caused by holding the resonance body or by applying the resonance body, or by parts which are in unmuffled contact with the resonance body, generate distracting noises and interferences. There is an additional problem because of differences in the contact pressure of the stethoscope on the body surfaces, the reproducibility of the auscultated signals is not always assured.
The signals emanating from the physician are transmitted through his or her hand to the stethoscope head and result in interfering overlaid extraneous signals.